1. Field of the Invention
The present invention relates primarily to electrophotographic reproduction apparatus and methods and, more specifically, to improvements in reproduction of documents some of which have more than one color.
2. Brief Description of the Prior Art
In the prior art as described in U.S. Pat. No. 4,655,579 an electrophotographic reproduction apparatus is described for reproducing an original document of one or more colors. As the original document is optically scanned onto each of four image frames a sensor senses the color content of the original and erases areas of image frames that are not to be developed. For example, a black only original will ordinarily be imageable upon each of the image frames that are to be developed with cyan, magenta, yellow and black toner. However, in response to the signals from the sensor the image frames to be developed with cyan, magenta and yellow are all erased of charge prior to development so that development of the image is provided only on the image frame developed in black. While this produces a true black reproduction, rather than a "process" black reproduction, i.e., a reproduction of black using superimposed cyan, magenta, and yellow toners, the reproduction process is slow as it requires four separate scannings of an original.
It is therefore an object of the invention to provide method and apparatus for improved productivity of reproducing originals, some of which have color content.